The leading ignition protection type is critical for the electrical connection of a pressure sensor with explosion protection. It generally does not necessarily have to be the main one with the stricter requirements. This applies, for example, for the UHP pressure transducers of the WU series from WIKA. They have been designed for used in semiconductor production.
Explosion protection is an indispensable safety precaution there. For the reason that the substances necessary for manufacturing include highly flammable gases. Consequently, there is a threat of an explosive atmosphere forming.
Explosion protection concept
UHP pressure transducers for such processes must be designed with the corresponding safety. In addition to their small design and specific process connections, the models WUC-1x and WU-2x have a comprehensive explosion protection concept. The marking of the instruments provides info on this:
II 3G Ex ec ic IIC T6/T5/T4 Gc X
The abbreviations listed in them mean, in more detail:
II 3G:
Equipment group 2 (all areas except mining), can be used in zone 2 (rare and short-term Ex atmosphere).
Ex ec ic:
Ignition protection types ?ec? (increased Indulgent ) and ?ic? (intrinsically safe; zone 2).
?Ex ec? has replaced the ignition protection type ?Ex nA? (non-sparking) since the start of 2022. However, this will not affect the Ex idea of the instruments.
IIC:
Explosion group (here: gases, resistive ignition energy of 40 �J, suitable for hydrogen/acetylene).
T6/T5/T4:
Temperature classes. T6 because the highest requirement means a maximum permissible surface temperature in the Ex environment < 85 �C (max. surface temperature of the WUC-1x and WU-2x: 40 �C).
Gc:
?Equipment Protection Level? (EPL) for zone 2 per IEC 60079-0
X:
Specific requirements which are listed in the operating instructions (for instance, the suitable mating connector).
?ec? is the leading ignition protection type
It really is noticeable that the marking contains two ignition protection types. However, only one is relevant for the electrical connection: the best ignition protection type. In the case of the pressure transducers from the WU series, this can be the Ex ec (Ex nA around 2022) mentioned first and not the stricter Ex ic. This may also be seen in the bond values in the info sheet and operating instructions. Only the specification of the utmost supply voltage UN = 30 V, that is also stated in the IECEx certificate, is relevant here.
What does the classification ?Ex ic? are a symbol of? It only pertains to the potentiometer of the transducer. The resistive component has an intrinsically safe circuit and may therefore be adjusted to correct zero drift during operation. Within their overall form, the WU models usually do not require an intrinsically safe circuit. However, they need to never be disconnected from the circuit during operation or when an Ex atmosphere is present.
Note
More info on the WUC-1x and WU-2x UHP pressure transducers and about hydrogen can be found on the WIKA website. In case you have any questions, your contact will gladly help you.
Also read our articles
Ex protection: The most common ignition protection types for sensors in gas hazardous areas
Ex protection: The difference between your zone and division model